Workers are thought to have downed tools on a North Sea oil rig in a protest against alleged poor working conditions.

A group of offshore whistle-blowers have posted messages on social media claiming 200 employees from Aker Solutions are undertaking an “unofficial” four hour “sit in” on the Mariner installation this morning.

They also claimed a number of staff members from Stork are involved.

As the supposed action is “unofficial”, it is understood trade unions have not organised the walkout.

A spokesman for the group said: “Lockdown on Mariner hook up as workforce bite back. Tomorrow brings a day of unofficial action against working conditions on the Mariner hook up.”

The spokesman has also published a picture, above, appearing to show large numbers of workers sat in a social area on the platform refusing to work.

The spokesman said crew were tired of “getting treated like dirt”.

A spokesman for Aker Solutions said: “We have been made aware that some workers based at the Mariner field have chosen not to work today. The company has received no official notification of this activity and is looking into this matter.”

Mariner-operator Statoil and Stork have also been contacted for comment.